PDMS-chemistry of angiotensin II and insulin in glucose glass thin films.

A plasma desorption mass spectrometry study was made on the properties of glucose and glucose/glucuronic acid thin films as matrices for amino acids, small and large peptides and insulin. Amino acids and small peptides are distributed throughout the film as it is formed from aqueous solutions and the mass spectra are similar to what is observed for nitrocellulose matrices. AngiotensinII (angII), insulin, and reduced insulin containing the separated A- and B-chains concentrate at the surface of the film due to the hydrophobic interaction. Extensive positive and negative fragmentation patterns are observed for angII using the glucose glass film. The fragment ions appear to be formed from layers just below the surface of the film. The co-matrix of glucuronic acid/glucose produces a higher molecular ion yield. The spectrum of insulin in glucuronic acid/glucose consists mainly of positive ions with a fragmentation pattern from the B-chain. The spectrum of reduced insulin using a nitrocellulose matrix gives B-chain ions but glucose/glucuronic acid gives A-chain ions in both the positive and negative ion spectra. The fragmentation patterns of the A-chain and B-chain ions are sensitive to the nature of the matrix. An extensive negative ion A-chain fragmentation pattern was observed with glutamate ions serving as the charge centers. The reasons for the behavior of the A- and B-chain fragmentation patterns in these matrices is not clear.